Recently, most notebook computers have built-in image pickup devices for taking photographs or holding video conferences. With increasing development of digital techniques, text documents are gradually created as electronic files. Generally, text documents are scanned by scanning apparatuses and then saved as electronic files such as PDF (Portable Document Format) files. In a case that no scanning apparatus is connected to the notebook computer, the images of simple documents such as single-sided papers or business cards could be captured by the built-in image pickup device. The images captured by the built-in image pickup device are usually saved as JPEG (Joint Photographic Experts Group) files. Most users prefer using scanning apparatuses to scan the text documents as PDF files because the texts and signs contained in the PDF files are readable by the computer systems and could be converted as editable text files.
As known, optical character recognition (OCR) is a process of capturing an image of a document and then extracting the texts from that image. Recently, it is possible to analyze images that are captured from the image pickup device by the OCR technique and saved as JPEG files. As a consequence, individual texts or signs contained in the JPEG files are recognized and converted as editable text files. Since the associated OCR techniques are well established, the image pickup device is gradually adopted to obtain electronic files of the documents.
When an image pickup device of a notebook computer is used to capture the image of a document, some difficulties possibly occur. For example, the image pickup device of a typical notebook computer has a focal length of approximately 60 centimeters. If the distance between the image pickup device and the document is shorter than the preset focal length (i.e. 60 centimeters), the obtained image of the document is usually blurred and thus fails to be recognized by the naked eyes.
For using the image pickup device to obtain a sharp image of the document, an external lens is arranged in front of the image pickup device. The use of the external lens could shorten the preset focal length of the image pickup device in order to capture the image of the nearby document. An example of the external lens is a close-up lens. For mounting the close-up lens in the front of the image pickup device, a fastening device is necessary for connecting the close-up lens with the image pickup device.
FIG. 1 is a schematic side view illustrating a notebook computer having a fastening device according to the prior art. As shown in FIG. 1, the notebook computer 1 comprises a base 10 and an upper cover 11. A keyboard 101 is mounted on the base 10. Via the keyboard 101, the user may input characters or signs. The upper cover 11 comprises a screen 111 and an image pickup device 112. The image pickup device 112 is disposed on an upper edge of the upper cover 11 for capturing an image of a document. The screen 111 is used for showing the operating conditions of the notebook computer 1. In a case that an image is captured by the image pickup device 112, the image is shown on the screen 111. As shown in FIG. 1, the fastening device 12 comprises a hooking element 121, which is attached onto the upper cover 11 of the notebook computer 1. After the hooking element 121 is attached onto the upper cover 11, the fastening device 12 is connected with the notebook computer 1. Since the external lens 13 is connected with the fastening device 12, the external lens 13 will be arranged in front of the image pickup device 112.
Since the fastening device 12 is made of plastic material and has a specified configuration (e.g. the configuration of a hooking element or a clamping element), the process of making the mold of the fastening device 12 is complicated and not cost-effective. Moreover, in a case that the notebook computer is used in other places, the user should additionally carry the fastening device 12 in order to perform the image-capturing operation. In other words, it is very troublesome to simultaneously carry the notebook computer and the fastening device 12.